The correct answer is D. Lactic acid.
Sour milk is milk that has been fermented by lactic acid bacteria. These bacteria convert the lactose in milk into lactic acid, which gives sour milk its characteristic sour taste. Lactic acid is also a natural preservative, which helps to keep sour milk from spoiling.
Acetic acid is the main component of vinegar. It is a colorless, sour-tasting liquid that is used as a flavoring agent and preservative. Tartaric acid is a white, crystalline solid that is found in many fruits and vegetables. It is used as a flavoring agent and preservative, and it is also used in the production of baking powder and cream of tartar. Citric acid is a white, crystalline solid
that is found in citrus fruits. It is used as a flavoring agent and preservative, and it is also used in the production of soft drinks and other beverages.In conclusion, sour milk contains lactic acid, which is a natural preservative that gives sour milk its characteristic sour taste.